1. Field of the Invention
The present invention relates to the manufacture of a torus and, more particularly, to a method of manufacturing arcuate pistons from said torus for use in rotary actuators.
2. Description of the Prior Art
Rotary actuators are widely used in a variety of applications to rotate a driven member around a fixed axis. For example, rotary actuators are used to open and close valves, turn switches off and on, actuate steering mechanisms, etc. Rotary actuators are more desirable than so called linear actuators in many respects primarily because they are cable of producing greater torque and are more compact and lightweight.
As is well known, a rotary actuator basically comprises a housing which has an arcuate chamber, more specifically, a chamber in the form of a toroidal arc segment and a complimentary shaped arcuate piston which oscillates in the chamber in response to fluid pressure The piston is thus a segment of a torus.
The prior art rotary actuators, despite their efficiency, compactness and lightweight, suffer from a number of drawbacks. For one, it is difficult to provide a durable and efficient seal between the piston and the walls defining the arcuate chamber. As a practical matter, it is virtually impossible to cast a piston or a torus from which the pistons can be cut with the desired dimensions within the desired tolerances such that an effective seal can be achieved between the piston and wall defining the arcuate chamber. While it is possible to machine a roughly cast piston or torus into very close tolerance by the use of complicated and expensive machining apparatus such as a five-axis NC machine, such machining makes the cost of producing the torus or piston prohibitive.